michaud



(No Model) A. MIOHAU-D.

- PROGESS OF AND MEANS FOR PHOTO-ENGRAVING METALLIC PLATES. No. 254,998Patented Mar; 14,1882.

. lVZ/izamm. [722] i UNITED STATES PATENT Osmotic.

ALFRED MIOHAUD, OF PARIS, FRANCE.

PROCESS OF AND MEANS FOR PHOTO-ENGRAVING METALLIC PLATES.

SPECIFICATION forming part of Letters Patent No. 254,998, dated March14-, 1882. Application filed September 3, 18B]. (No model.) Patented inFrance July 11, 188i.

T all whom it may concern:

Be it known that I, ALFRED MICHAUD, of Paris, France, have invented aProcess of Engraving Metallic Plates to be used for Printing andOrnamental Purposes; and I do hereby declare that the following is afull, clear, and exact description of the same, reference being had tothe annexed sheet of drawings, making a part of the same.

My invention relates to a new process of engraving, consistingin the useof special metallic plates, which I shall afterward describe. Theapplication of these plates (for which I have filed an application atthe same time as the present one) is effected by a process known asphoto-engraving, and which I call galvano-en gravi'ng or physicalengraving, and which I will now proceed to describe.

Supposing it be desired to makean engraving on no matter what scale,after nature or after a painting or a pen or pencil drawing, 829 Iproceed as follows: I either,having previously prepared a suitablesupply of my metallic plates, which have the smoothness and polish ofglass, and having obtained a photographic negative of the subject to beengraved on a glass plate, cover one of the said polished plates with abichromated gelatine film, place the photographic negative upon it, andexpose them to the light. The action of light renders the gelatineinsoluble, so that when the negative is removed and the gelatine platewashed all the gelatine on the surface of the plate will be removed,except the duplicate of the lines or tracings of the photograph, whichwill remain in relief on the said polished plate. Or on the photographicnegative itself, covered with gummy varnish mixed with one per cent. ofbichromate ot' potash, I pour a determined quantity of bichromatedgelatine. This is then allowed to dry, its back is exposed to the light,and on being subsequently developed in warm water it gives the gelatineproof in relief. When dry this proof is placed for some hours 1n a dampplace. For instance, it may be shut up in a box, at the bottom of whichis placed wct paper. This wet paper is separated from the proof by a rowof glass tubes. The proof is then coated with plumbago, laid 50 on witha brush, after which it is applied to a melted alloy placed in a specialvessel. This alloy is then subjected to an ordinary pressure, and oncooling produces a hollow metallic plate or mold, ready to be printed.The fusible alloy which I preferably employ consists of bismuth, tin,lead, and mercury,iu proportions varying according to the degree ofhardness desired to be obtained in the mold.

The special vessel used to contain the melted metal is constructed asfollows: It is made in the form of a frame, A B, (see theaccompanyingdrawing, showinga plan view,) jointed atA and B by means ofcross-pieces 0, provided with wedges. The cross-piece shown at B isfurnished with an eccentric handle, 1?, so that the two halves of theframe may be joined at will. Between these two halves is placed a smoothand strong metallic plate, which serves asa bottom, D. The liquid metalis poured into a vessel thus constructed, and the gelatine proof isimmediately applied on the said metal, and the whole being covered by asecond thick metallic plate, which closes the vessel, it is put undermomentary pressure. When the metal has cooled the frame is removed, soas to separate the two iron plates containing the proof and the metallicmold produced by said proof,

and which are easily separated one from the other.

The hollow mold of fusible metal thus obtained is quite ready forprintingthat' is to say, it can be used for producing, first, transferon stone; second, transfer on metal for obtaining either typographicblocks by the ordinary means or hollow plates by thephoto-chemicalprocess; but ifthis metallic mold be placed in a galvanic bath of coppera relief is obtained capable of reproducing galvanically an indefinitenumber of hollow metallic plates, which may either be silvered or giltand used as mock 9o jewelry; or it may be used for copper-printing.

To return to the proofs obtained by the use of bichromated gelatine.These proofs are of two kinds. Ifthe photographic negative usedrepresents merely outlines, it may be employed 5 at once without anypreparation. If, on the contrary, it represents a photograph taken fromnature or from a half-tone drawing or painting, it is first of allcovered with a thin film, which produces the grain of the impres- I00sion, and which is transferred by insolation to the gelatineproot', andconsequently to the plate from which the print is produced. I producethe said grain as followsrI uniformly cover a piece of glass, ofvariable dimensions, with a gummy liquid, and I introduce this piece ofglass into a box or case containing the opaque powder which forms thegrain, and which box or case has been previously well shaken ineverydirection. By means otthet-ype or types thus made 1 insolate asheet of paper treated 4 with colored and biehromated gelatine. I applythis sheet on the photographic negative, which is covered withbichromated gum varnish, and I develop the same in warm water, whichdraws off the non-insolated gelatine, leavingtheinsoluble parts whichform the grain. It is evident thatin place of this uniform grain it iseasy to produce another grain for photographic negatives, either byartistic work or mechanically, by using metallic wires, 850.,

combined in various ways, so as to produce the kind of engraving whichis indispensable in copper-prin ting.

I claim 1. The combination, with the frame A B, provided with theslotted and jointed ends A B, and the removable plates D, of the slottedcross-pieces 0, provided with wedges, and the eecentrical handle P,substantially as and for the purpose set forth.

2. The process herein described of producing a metal mold in relief,consisting in applying a gelatine bichromatic proof, formed by theprocess above described, to the surface of a melted alloy in a closevessel and subjecting it to pressure, as set forth.

ALFRED M-ICHAUD.

Witnesses:

R0121. M. HoorER, ALBERT MOREAU.

